Fluid mixer and water oxygenator incorporating same

ABSTRACT

A fluid mixer includes an elongate mixing chamber having an inlet system at one end for admission of liquid and gas to be intimately mixed by passage through the chamber and an outlet for the mixture at the opposite end, wherein opposed longitudinal sides of the chamber are each defined by a surface of scallop shape having peaks and troughs, with the peaks of the two surfaces being relatively offset so as to cause the liquid and gas entering the chamber to flow along a generally sinuous path through the chamber to create a turbulent flow which promotes intimate mixing. Advantageously a UV source extends within the chamber to sterilize the liquid flowing through the chamber.

The present invention relates to fluid mixers, for example for use inmixing liquids, or liquids and gases.

A particular application of the invention is in mixing oxygen or airwith water for cleaning the water in a swimming pool without the needfor chlorine.

In the cleaning of water for use in swimming pools it is known to addchlorine. This has the disadvantage that chlorine is a poison and manypeople develop skin problems from long exposure to chlorinated water inswimming pools. In some countries, such as USA and Germany, the use ofchlorine in swimming pools has been banned and instead ozone treatmentis used. A disadvantage of ozone treatment is that an extremely largeamount of energy is required to generate sufficient ozone to treat thewater, and then to ensure that there is no ozone remaining in the waterwhen it is returned to the swimming pool.

We believe that the main cause of contamination of water in a swimmingpool is due to anaerobic bacteria. One method of dealing with thiscontamination is to introduce air or oxygen at sufficiently highconcentrations as to saturate the water which then kills the anaerobicbacteria. In addition UV radiation can be applied to the water todestroy other contaminants and other forms of biological material. Wealso believe that a significant factor in achieving good treatment ofthe water with the use of air/oxygen and UV radiation involves the useof a mixer which will vigorously mix the gas and liquid and bring all ofthe water into close proximity to the UV radiation.

According to one aspect of the present invention, there is provided afluid mixer including an elongate mixing chamber having an inlet at oneend for admission of fluid and an outlet at an opposite end, the chamberhaving in longitudinal cross-section an interior profile which, whenconsidered along a longitudinal plane, consists of a series of troughsand peaks at each side of the longitudinal axis and extending along thelength of the chamber, the series of troughs and peaks being at theopposite sides of the longitudinal axis being relatively displaced sothat the peaks of the profile along one side face the troughs of theprofile along the other side, the configuration of the troughs and peakscausing fluid entering the chamber through the inlet to flow along atortuous path through the chamber towards the outlet to create aturbulent flow which promotes intimate mixing within the fluid.

According to another aspect of the present invention, there is provideda fluid mixer comprising an elongate mixing chamber having an inletsystem at one end for admission of liquid and gas to be intimately mixedby passage through the chamber and an outlet for the mixture at theopposite end, wherein opposed longitudinal sides of the chamber are eachdefined by a respective series of concave surfaces spaced longitudinallyof the chamber, with the concave surfaces at the opposite sides being soconfigured as to cause the liquid and gas entering the chamber to flowalong a generally sinuous path through the chamber to create a turbulentflow which promotes intimate mixing.

According to yet another aspect of the present invention, there isprovided a water steriliser and oxygenator including an elongate mixingchamber having an inlet at one end and an outlet at an opposite end, aninlet system coupled to the inlet and comprising a venturi through whichincoming water flows, said venturi having a throat communicating with anair inlet whereby air is drawn into the venturi by the water flowingtherethrough, sterilising means extending longitudinally within themixing chamber, the mixing chamber having opposed longitudinal sideseach profiled to define a series of troughs of arcuate cross-sectionspaced along the length of the chamber, with the troughs along one sidebeing longitudinally offset with respect to the troughs along the otherside whereby the water is caused to flow through the chamber along apath which traverses repeatedly from one side of the chamber to theother with a turbulent flow which promotes intimate mixing of the waterand air, and parts of the troughs relatively close to the sterilisingmeans confine the liquid flow past those parts to zones relatively closeto the sterilising means to promote effective sterilisation.

According to yet another aspect of the invention, there is provided afluid mixer including an elongate mixing chamber having an inlet systemat one end for admission of liquid and gas to be intimately mixed bypassage through the chamber and an outlet for the mixture at theopposite end, wherein opposed longitudinal sides of the chamber are eachdefined by a surface of scallop shape having peaks and troughs, with thepeaks of the two surfaces being relatively offset so as to cause theliquid and gas entering the chamber to flow along a generally sinuouspath through the chamber to create a turbulent flow which promotesintimate mixing.

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view, seen from above, of a fluid mixer inaccordance with a preferred embodiment of the present invention;

FIG. 2 is a cross-sectional side view of the fluid mixer of FIG. 1, withan oxygen injector fitted at its upstream or inlet end;

FIG. 3 is a cross-sectional view of the fluid mixer taken on line 3—3 ofFIG. 2;

FIG. 4 is a cross-sectional side view of the fluid mixer of FIG. 1, witha venturi injector fitted at its upstream or inlet end;

FIG. 5 is a cross-sectional view of the fluid mixer of FIG. 4 taken online 5—5; and

FIG. 6 is a part cross-sectional side view of the fluid mixer of FIG. 1showing schematically the nature of the mixing which is produced.

In the drawings there is shown a fluid mixer 10 in the form of anoxygenator for mixing air or oxygen into water, particularly, but notexclusively, for use in the treatment of swimming pool water as asubstitute for chlorine.

The fluid mixer 10 comprises a housing 20, an inlet pipe 22, an outletpipe 24 and a UV source 26 extending longitudinally in a mixing chamberwithin the housing. The housing 20 is elongate and substantiallyrectangular in external cross-section. The housing 20 has an inlet 30connected to the inlet pipe 22 and an outlet 32 connected to the outletpipe 24. The housing 20 has an elongate mixing chamber 34 which definesa generally sinuous or tortuous path. for the flow of fluid from theinlet 30 to the outlet 32.

Preferably, the housing 20 is made from a plastics material which isresistant to corrosion by UV and ozone, such as, for example,polycarbonate, polypropylene, polyethylene or the like. Typically, thehousing 20 is translucent or opaque.

In the embodiment shown, the chamber 34 has two opposing side walls 36which have a substantially sinuous profile and two connecting side walls38 which are substantially planar. The sinuous side walls 36 each havepeaks 40 and troughs 42. The troughs 42 are of arcuate cross-section asconsidered in a longitudinal plane (for example the plane of FIGS. 2, 4and 6) and are preferably of part-cylindrical shape between the sidewalls 38 as can be seen from FIG. 1. Each peak 40 connects the inner endedges of two adjacent troughs 42 and is of very small lengthlongitudinally in comparison with that of the troughs 42 so that, ineffect, the peaks 40 form cusps between adjacent troughs 42. Expresseddifferently, the sinuous side walls 36 have a shape which is defined bya substantially cosine squared mathematical function, with the zeropoints of the function (corresponding to the peaks 40) being curvedtightly instead of being pointed. Such a shape may also be referred toas scallop shaped. The two sinuous side walls 36 are offset with respectto each other so that the peaks of one of the sinuous side walls 36correspond to the troughs 42 of the other sinuous side wall 36.

The effect of the shape of the opposing side walls 36 of the chamber 34is that the fluid entering the housing 20 at the inlet 22 follows fluidpaths 50, 52 and 54 (see FIG. 6). The fluid path 50 represents the mainpath of fluid flow along which the bulk of the volume of the fluidtravels. It is important to note that the fluid path 50 comes into closeproximity to the UV source 26 many times (as shown about 15 times) alongthe length of the chamber 34. This has the effect that the bulk of thevolume of the fluid comes into close proximity with the UV radiation arelatively large number of times along the chamber 34. Advantageously,the configuration of the chamber 34 is such that the bulk of the fluidperiodically passes to about 5 mm or less from the UV source whichpromotes effective radiation.

The fluid paths 52 are detaching flows of the fluid which leave contactwith the sinuous side walls 36 at the peaks 40 and force the fluid path50 to change its direction and re-cross the UV source 26.

The fluid paths 54 are eddies which are caused by the separation of thefluid paths 52 from the sinuous side walls 36. The eddies add to themixing effect of the fluid mixer 10.

These three fluid paths 50, 52, 54 have the effect of causing intimatemixing of the fluids entering into the chamber 34. At the same time thethree fluid paths 50 to 54 have the effect of bringing the mixed fluidsinto intimate contact with the UV source for increasing the efficacy ofirradiation of the fluids.

The housing 20 has a cap 60 which holds the UV source 26 in the chamber34 and seals the chamber 34 so that it is fluid tight. Preferably,O-ring seals are used between the UV source 26 and the cap 60 and thehousing 20 for this purpose. The UV source 26 comprises a UV elementmounted within a tube. Preferably, the UV source 26 operates atwavelengths of about 254 nm (for producing a germicidal effect) and 180nm (for the production of elemental oxygen and ozone). In one practicalexample the UV source has a power consumption of about 0.075 kW ofelectricity for use in a chamber which is about 860 nm long, about 50 mmwide and about 50 mm deep. Preferably, the UV source is located about 5mm from the peaks 40 of the side walls 36 so as to ensure that the fluidcomes into close proximity to the UV source 26 as it flows through thechamber 34.

In the embodiment of FIG. 2 a sparger 70 is located in the inlet pipe22. The sparger 70 includes a screen for producing very small bubbles.The sparger 70 is connected to a supply of oxygen gas- such as bottlesof oxygen stored under high pressure. Hence, the sparger 70 serves toproduce a very large number of very small bubbles of oxygen into thestream of liquid (water) which is introduced into the inlet pipe 22.

In use, the inlet pipe 22 is coupled to the outlet of a swimming poolpump and the outlet pipe 24 is connected to a water return pipe of aswimming pool. The sparger 70 is connected to a bottle of oxygen gas.Water entering the inlet pipe 22 flows past the sparger 70 whichdischarges a multiplicity of tiny bubbles of oxygen into the water. Thecombination of the water and the oxygen follows along the fluid paths50, 52, 54. In so doing the oxygen is mixed with the water and themixture is irradiated with the UV radiation. Where the UV radiationimpacts upon a molecule of oxygen, it converts it into two oxygen atoms.The oxygen atoms are highly reactive and either attach to another oxygenmolecule to produce ozone or oxidise other material which may exist inthe water. The ozone is also highly reactive and oxidises other materialwhich may exist in the water. Hence, the UV radiation has the effect ofincreasing the oxygenation of the water by adding to the oxidationeffect.

The highly oxygenated water exits out of the outlet 32 and returns intothe swimming pool and mixes with the water in the pool which increasesthe oxygen level generally in the swimming pool. When the level ofoxygen reaches saturation all of the anaerobic bacteria in the swimmingpool die. Also, other material in the swimming pool are oxidised.

We also believe that detritus material in the pool will tend to float tothe surface of the pool which allows more of the detritus material to beremoved by skimmer boxes and the like.

The embodiment of FIGS. 4 and 5 differs from that of FIG. 2 in that inplace of the sparger 70, the inlet pipe 22 incorporates a venturi 71having an air inlet 72 leading into its throat so that the water flowingthrough the venturi 71 will cause air to be drawn in via the inlet 72for admixture with the water. We have determined that air drawn into theinlet 72 directly from atmosphere will introduce sufficient oxygen foreffective treatment without the need to incorporate a dedicated oxygensupply, such as oxygen bottles and, therefore, this method is preferredin a practical sense. A control valve can be incorporated upstream ofthe inlet 72 to regulate the amount of air drawn in. Instead of drawingthe air directly from atmosphere into the inlet 72, the inlet 72 can becoupled by a pipe 74 to a thin quartz tube 76 within the interior of theouter tube of the UV source. The quartz tube 76 allows air to be drawnthrough the UV source 26 via the cap 60. The air in the quartz tube 76is irradiated with UV light which causes some of the oxygen in the airto be converted into elemental oxygen and ozone.

The mixer of the preferred embodiment has the advantage that intimatemixing of the fluids is created by using a chamber which develops thefluid paths 50, 52, 54. This mixing has the added advantage that ittakes place in close proximity to the UV source 26 which increases theefficacy of the UV radiation and hence leads to better treatment of thefluid. The particular form of the fluid paths within the chamber isdetermined by the described shaping of the opposed side walls 36 andthis shaping not only provides intimate mixing but achieves this effectwithout creating a significant pressure drop across the chamber whichwould otherwise impair the efficiency of air injection using a venturias is preferred.

Where the fluid mixer 10 is used to treat water from a swimming pool itobviates the need to use chlorine. Also, we believe that since the wateris super-oxygenated it will require much less time in treating the waterthan conventional filter systems which are based on chlorine. Further,since it is only oxygen it is safe to use the treatment whilst peopleare using the swimming pool which is in contradistinction to theapplication of ozone into swimming pools (where it is preferred thatmeasures be taken to ensure that no ozone enters the pool whilst peopleare using it, or alternatively, the treatment of the water in the poolonly happens when there are no people in the pool).

Modifications and variations are within the scope of the presentinvention. For example, two or more of the fluid mixers could bearranged in parallel in order to allow a greater rate of flow. In such acase, manifolds would be used to connect the fluid mixers to a commoninlet pipe. Also, two or more of the fluid mixers 10 could be arrangedin series in order to increase the duration of the UV treatment and thelike. Further, the fluid mixer could be adapted for other forms ofconditioning treatment where mixing is important. For example, thetreatment could involve cooling by using a refrigerant source in placeof the UV source or heating by using a heating source. As a furtheralternative a silver rod could be used and the interior of the chamber34 could be coated with copper so as to ionise the fluid; other ionisingmaterials could also be used.

The fluid mixer particularly described also has other significantapplications involving the oxygenation of water by intimate mixing,without involving the use of additional conditioning treatment such asUV irradiation. For example the mixer can be used in a system forremoving iron from solution, wherein the intimate mixing of the waterwith air facilitates subsequent precipitation of the iron in a holdingtank. The mixing action within the mixer also has been found toaccurately control and stabilise the pH to approximately 7.2 due to a“stripping” action which takes place wherein the air travels through thewater at a greater velocity than the water velocity. The mixer can alsobe used as part of the feed system within hydroponic agriculture.

Other modifications and variations are possible within the scope of theinvention.

Throughout this specification and claims which follow, unless thecontext requires otherwise, the word “comprise”, and variations such as“comprises” or “comprising”, will be understood to imply the inclusionof a stated integer or group of integers or steps but not the exclusionof any other integer or group of integers.

What is claimed is:
 1. A fluid mixer including an elongate mixingchamber having an inlet at one end for admission of fluid and an outletat an opposite end, the chamber having two opposed longitudinal sidewalls each of which consists of a series of troughs and peaks at eachside of the longitudinal axis of the chamber and extending along thelength of the chamber, the series of troughs and peaks at opposite sidesof the longitudinal axis being relatively displaced so that the peaks ofthe profile along one side face the troughs of the profile along theother side, the troughs being of generally part-cylindrical shape andthe peaks being cusps of generally rectilinear form, fluid conditioningmeans mounted within the chamber and extending longitudinally within thechamber for conditioning the fluid as it passes through the chamber, thecusps lying close to the conditioning means so as to cause the fluid topass close to the conditioning means at periodic intervals duringpassage through the chamber, and the configuration of the troughs andcusps causing fluid entering the chamber through the inlet to flow alonga tortuous path through the chamber towards the outlet to create aturbulent flow which promotes intimate mixing within the fluid.
 2. Afluid mixer according to claim 1 including means for feeding a liquidand a gas into the inlet to be mixed intimately by passage through themixing chamber.
 3. A fluid mixer according to claim 2, wherein theliquid is water and the gas is an oxygen-containing gas.
 4. A fluidmixer according to claim 2, wherein the feed means comprises a passageincluding a venturi through which the liquid flows, with a gas inletleading into a throat of the venturi.
 5. A fluid mixer according toclaim 1, wherein the conditioning means is a sterilizer, a cooler, or aheater.
 6. A fluid mixed according to claim 5, wherein the conditioningmeans is a sterilizer comprising a source of UV radiation mounted withina tube.
 7. A fluid mixer according to claim 6, wherein the tube includesan air inlet and an air outlet for air irradiated by the ultravioletradiation, said air outlet being coupled to the feed means.